Copper Lining Fitted & Vacuum Parts

After a many month hiatus, I’m back!! The programming job is finished and I am back on Levitee research full time (besides a bit of TOF work).

After a good many hours hand sanding and polishing the inside of the cavity, I ended up with this:

The extra solder at the top of the narrow end is because I was unfortunately a bit overzealous with the high powered sander and had to refill the seams.  I did, however, use a solder that was %50 silver which has better conductivity then regular tin solder.  I then sanded everything down ending with a wet 600 grit sand paper to get all the surfaces as smooth as possible and to take off any copper oxide and/or flux that had built up.

I then mated the copper and plastic shell:

(The end pieces still have the plastic covering which I will remove just before testing and the circular copper tuning plate still has to be soldered to the square piece. )

The plastic shell has been an excellent idea because it has proved invaluable for numerous reasons:

  • The plastic shell is computer generated right from design to fabrication and it is as near to perfection as economically possible
  • It is an excellent tool to measure the copper before soldering it.
  • Once soldered and worked, the copper takes up an unsymmetrical shape but the plastic shell forces it back.

The copper sticks out the bottom of the plastic shell more then enough, but I am having difficulty getting it to stick above the top, where it needs to touch the top plate for grounding purposes.  It is only a few millimetres too low  The problem is that the irregularities of the bottom means I can’t slide the shell down far enough.  In the future, I would cut the copper at the narrow end another couple of centimetres higher in order to make fitting it back into the plastic shell easier.  More height at the top would also mean more travel for the tuning plate if necessary.  I will probably have to put a bead of solder around the edge of the top plate in order to make sure it touches the copper inside the cavity.

I have also moved back out into the garage and here is a shot from the footage as I was demonstrating something:

That’s a crokinole board face down on the wet cutting table!

I was also up at the university last week working on the vacuum chamber and I think I have the last bits figured out:

  • I can get the blank 1.33″ seals I need for $17 each.
  • To get the microwaves into the cavity I use one of these:

    Which can handle 5KV and has an N-type connector on one side.  I then have to figure out how to connect it to the microwave cavity inside the vacuum chamber.. Hmmm.. I might need a type with N connectors on both sides…  I am also not sure the flange size is right, but it was only $40 to order it (used) and I will know in a week or so.  The flange should fit because according to this MDC page, the Del-Seal CF metal seal flanges, which is what I have, are compatible with Varian.
  • Then to connect the roughing vacuum pump, I use one of these:

I also noticed that two vacuum chambers about the same size as the one I bought went through eBay for a paltry couple hundred each!  One here and one here (eBay links removed).  I paid $2600 for mine, although mine is aluminum, has a turning mechanism that might prove useful and struts on the side to mount it.